Ultrasound scanner and method of operation

ABSTRACT

Battery-powered ultrasound scanner for veterinary applications, and operating method. Ultrasound measurements are processed to determine if an ultrasound probe is not being moved and, if it is not being moved, the average rate at which ultrasound pulses is generated, thereby reducing power consumption. The average rate at which ultrasound pulses are generated is reduced step-wise if non-movement persist but increase rapidly when movement recommences.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a Continuation Application of U.S.Nonprovisional patent application Ser. No. 15/907,974, filed Feb. 28,2018, which claims priority to GB Application No. 1703253.3, filed Feb.28, 2017, the disclosures of which are incorporated herein by referencein their entirety.

FIELD OF THE INVENTION

The invention relates to the field of ultrasound scanners for medical,particularly veterinary, ultrasound imaging applications.

BACKGROUND TO THE INVENTION

Portable battery-powered veterinary ultrasound scanners are often usedin challenging environments, for example outdoors, or in farm buildings,over extended periods of time. Power consumption can be significant andbattery lifetime is important. The present invention aims to address theproblem of reducing power consumption in a portable battery-poweredultrasound scanner. Reducing power consumption can enable a smallerproduct size, particularly in a rugged product design with limitedcooling (e.g. without a fan).

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is a provided an(e.g. veterinary) ultrasound scanner, the ultrasound scanner comprising:

-   -   an ultrasound probe which comprises one or more ultrasound        sources and receivers,    -   at least one battery,    -   transmit circuitry configured to apply electrical signals to the        ultrasound sources to generate ultrasound pulses and transmit        them into a scan region,    -   receive circuitry configured to measure ultrasound echoes        received at the ultrasound receivers from the scan region,    -   a beam processor configured to process the measured ultrasound        echoes and output ultrasound measurement data, the ultrasound        measurement data comprising measurements of ultrasound echoes        from each of a series of scan positions in the scan region,    -   a controller configured to regulate the transmission of        ultrasound pulses into the scan region by the ultrasound source        and to process the ultrasound measurement data, or data derived        therefrom, to determine an amount of movement of the ultrasound        probe, and to reduce the average rate at which ultrasound pulses        are generated responsive to the determined amount of movement of        the ultrasound probe meeting at least one inactivity criterion.

The invention extends in a second aspect to a method of operating an(e.g. veterinary) ultrasound scanner, the ultrasound scanner comprisingan ultrasound probe which comprises one or more ultrasound sources andreceivers, (the ultrasound scanner typically also comprising at leastone battery), the method comprising:

-   -   the one or more ultrasound sources and receivers generating        ultrasound pulses and receiving ultrasound echoes from a scan        region,    -   processing measurements of the received ultrasound echoes to        thereby calculate ultrasound measurement data, the ultrasound        measurement data comprising measurements of ultrasound echoes        from each of a series of scan positions in the scan region,    -   processing the ultrasound measurement data, or data derived        therefrom, to determine an amount of movement of the ultrasound        probe,    -   if the amount of movement of the ultrasound probe thereby        detected meets at least one inactivity criterion, reducing the        average rate at which ultrasound pulses are generated.

Thus, when it is determined from the ultrasound measurement data, ordata derived therefrom, that the at least one inactivity criterion ismet, the average rate at which ultrasound pulses are generated isreduced. This reduces power consumption by the transmit circuitry (andin some embodiments by the receive circuitry, beam processor and/orcontroller).

This contrasts with detecting that an ultrasound probe is no longer inphysical contact with a subject by, for example, detecting the absenceof ultrasound echoes and so enables power consumption to be reduced ifan ultrasound probe is not being moved, even if it does remain inphysical contact with a subject. It may be that the ultrasound scanneris further configured to detect an absence of ultrasound echoes inresponse to ultrasound pulses and to enter a standby mode responsivethereto. The standby mode is a distinct mode. Typically, in at leastsome circumstances (e.g. mode) in which the average rate at whichultrasound pulses are generated, the average rate at which ultrasoundpulses are generated remains at least 10 times (and typically at least100 times) higher than the average rate at which ultrasound pulses aregenerated in the standby mode.

The ultrasound measurement data typically comprises data (samples)specifying the measured strength of ultrasound echoes received by one ormore ultrasound receivers from the corresponding position within thescan region. By the strength of ultrasound echoes we refer to aparameter relating to the intensity, amplitude or brightness of theultrasound echoes, in absolute terms or relative to the incidentultrasound pulses.

The one or more ultrasound sources and receivers may comprise an arrayof ultrasound sources and receivers. However, it is possible that one ormore ultrasound sources and receivers is mounted on a support and isswept repetitively along a path in use. In this case a single ultrasoundsource and a single ultrasound receiver (e.g. a single ultrasoundtransceiver) may be sufficient.

By scan positions we refer to positions relative to the one or moreultrasound sources and receivers (or the path along which the one ormore ultrasound sources and receivers are repetitively moved in use, asappropriate) and thereby relative to the ultrasound probe. The amount ofmovement of the ultrasound probe may be determined by analysing changesin the ultrasound measurement data, or data derived therefrom, betweenrepeated measurements of the same scan positions, for example:

-   -   by calculating a measure of changes in the strength of        ultrasound echoes between measurements (e.g. consecutive        measurements) of ultrasound echoes from one or more        corresponding positions (typically scan positions);    -   by processing the ultrasound measurement data, or data derived        therefrom, to detect one or more features within the scan region        (e.g. boundaries, internal cavities, or points of unusually        strong or weak echoes) and processing subsequently obtained        ultrasound measurement data, or data derived therefrom, (e.g.        measurement data relating to a subsequent ultrasound frame) to        determine whether and/or by how much, the one or more features        have moved (relative to the ultrasound probe);    -   by calculating a property of the strength of ultrasound echoes        at a plurality of positions (typically scan positions) from the        ultrasound measurement data, or data derived therefrom, for        example, calculating an average value (e.g. arithmetic mean,        median, mode, geometric mean), variance, standard deviation or        range of the strength of ultrasound echoes at a plurality of        positions (typically scan positions), and calculating a measure        of change in that value between measurements (e.g. consecutive        measurements) of the corresponding positions (typically scan        positions).

Thus the at least one inactivity criteria may comprise that a measure ofchanges in the strength of ultrasound echoes between measurements (e.g.consecutive measurements) of ultrasound echoes from one or morecorresponding positions (typically scan positions) is below a threshold,optionally for at least a predetermined period of time. The at least oneinactivity criteria may comprise that the position of one or morefeatures within the scan region determined from the ultrasoundmeasurement data or data derived therefrom, relative to the ultrasoundprobe (e.g. relative to the array of ultrasound sources and detectors,or the path along which the one or more ultrasound sources and receiversare repetitively moved in use, as appropriate), has moved by less than athreshold amount, optionally over at least a predetermined period oftime. The at least one inactivity criteria may comprise that a measureof a change in a property of the strength of ultrasound echoes at aplurality of positions in the ultrasound measurement data, or dataderived therefrom, (typically scan positions in the ultrasoundmeasurement data) is less than a predetermined threshold, optionally forat least a predetermined period of time. Said predetermined period oftime may, for example, be in the range of 1 to 30 seconds, typically 2.5to 20 seconds.

It may be that the average rate of generation of ultrasound pulses isreduced in response to detection that a measured temperature within theultrasound scanner exceeds a first threshold, typically until themeasured temperature decreases to below a second threshold (which is thesame or a lower temperature than the first threshold). The ultrasoundscanner may comprise a temperature sensor.

The ultrasound measurement data is typically divided into ultrasoundframes, each ultrasound frame comprising measurements of ultrasoundechoes at scan positions distributed across the scan region such that aplurality of ultrasound frames represents a plurality of measurement ofultrasound echoes across the scan region at different (typicallyconsecutive) time, and so can be used to generate consecutive ultrasoundimages of the scan region.

The scan region is typically scanned as a series of scan lines,extending from the array of ultrasound transmitters and receivers (orthe path along which the one or more ultrasound sources and receiversare repetitively moved in use, as appropriate) at different angles. Theplurality of scan positions in the scan region typically comprises aplurality of scan positions spaced apart (usually regularly) along eachof a plurality of scan lines which extend through the scan region atdifferent angles relative to the array of ultrasound transmitters andreceivers (or the path along which the one or more ultrasound sourcesand receivers are repetitively moved in use, as appropriate). Ultrasoundpulses may be focussed along individual scan lines in turn and therebypass through scan positions along a scan line in turn. Thus theultrasound measurement data is typically divided into ultrasound linedata portions which specify the measured strength (e.g. intensity ofamplitude) of ultrasound echoes received by one or more ultrasoundreceivers from a series of spaced apart position along a line (typicallya straight line extending from the ultrasound probe into the scanregion).

Typically, the ultrasound measurement data is divided into ultrasoundframe data portions (relating to separate ultrasound frames), each ofwhich represents measurements of ultrasound echoes across the scanregion, suitable for forming an image frame. In this case, eachultrasound frame data portion typically comprises a plurality ofultrasound line data portions extending through the scan region, e.g. atdifferent angles relative to the ultrasound probe (e.g. relative to thearray of ultrasound sources and receivers or the path along which theone or more ultrasound sources and receivers are repetitively moved inuse, as appropriate). It is not however necessary for each ultrasoundframe data portion to have ultrasound line data portions relating to thesame angles relative to the ultrasound receivers and transmitters, forexample, ultrasound line data portions relating to different scan lines(angles relative to the array of ultrasound sources and receivers (orthe path along which the one or more ultrasound sources and receiversare repetitively moved in use, as appropriate)) may be included inalternate ultrasound frame data portions.

There may be a main operating mode (e.g. a default mode or a modedetermined wholly or in part by user settings) in which there is apredetermined average rate at which ultrasound pulses are generated.When the average rate at which ultrasound pulses are generated isreduced, that is typically relative to that main operating mode.

The average rate at which ultrasound pulses are generated may be reduced(e.g. relative to a main operating mode) by one or more of:

-   -   reducing the number of scan lines (e.g. per ultrasound frame);    -   increasing the period between ultrasound frames;    -   periodically stopping generating ultrasound pulses for a period        of time and then restarting

It is better to reduce the number of scan lines, or increase the periodbetween ultrasound frames, which may cause a degradation of imagequality, than to lose continuity of imaging.

It may be that the average rate at which ultrasound pulses are generatedis reduced progressively, for example step-wise, responsive to thedetermined amount of movement of the ultrasound probe meeting at leastone inactivity criterion. The period of time taken to progressivelyreduce the average rate at which ultrasound pulses are generated may forexample be in the range of 1 to 30 seconds, for example 2 to 10 seconds.

It may be that the average rate at which ultrasound pulses are generatedis reduced, responsive to the determined amount of movement of theultrasound probe meeting at least one inactivity criterion, through aplurality of different modes which differ in the average rate at whichultrasound pulses are generated, in a predetermined order. The modes mayfor example differ in terms of one or more of: the number of scan linesper ultrasound frame and/or the period between ultrasound frames.

It is the average rate which is important. It may for example be that insome modes, when ultrasound pulses are generated they are generated ingroups and have the same period between pulses within each group, butthat that there are periodic (increased) gaps between groups ofultrasound pulses, thereby reducing the average rate of ultrasoundpulses generation.

It may be that in the main operating mode, ultrasound measurement data,or data derived therefrom, relating to a first number of scan positionsis processed to determine whether the at least one inactivity criterionis met but that in at least one mode with a reduced average rate ofgeneration of ultrasound pulses, a second, lower number of scanpositions is processed to determine whether the at least one inactivitycriterion, or at least one activity criterion, is met. Thus, fewerultrasound pulses required to be generated in the reduced powerconfigurations (modes) than would otherwise be the case in order todetermine when the average rate of ultrasound pulse generation shouldincrease again.

It may be that, in addition to reducing the average rate of generationof ultrasound pulses (e.g. in one or more reduced power modes) theintensity of ultrasound pulses is reduced.

It may be that, after reducing the average rate at which ultrasoundpulses are generated, the controller is configured to (after reducingthe average rate at which ultrasound pulses are generated) increase theaverage rate at which ultrasound pulses are generated again (for exampleentering the main operating mode) responsive to the determined amount ofmovement of the ultrasound probe meeting at least one activity criterion(for example, that an inactivity criterion is no longer met).

Thus, the method may comprise continuing to process the ultrasoundmeasurement data to determine an amount of movement of the ultrasoundprobe, and if the amount of movement of the ultrasound probe therebydetected meets at least one activity criterion, the average rate atwhich ultrasound pulses are generated is increased.

The average rate at which ultrasound pulses are generated may beincreased to the original rate (before the average rate was reduced),e.g. to the average rate of ultrasound pulses generation in the mainoperating mode (for example, by switching to the main operating mode).It may be that the increase in the average rate at which ultrasoundpulses are generated can take place during the scanning of an ultrasoundframe (and not only between the scanning of whole ultrasound frames). Itmay be that the increase in the average rate at which ultrasound pulsesare generated takes place in less than 1 second, for example less than0.5 or less than 0.25 seconds, for example.

It may be that, when the average rate at which ultrasound pulses aregenerated is reduced, the average rate at which ultrasound pulses aregenerated is reduced progressively (for example step-wise, such asthrough the said one or more modes), for example over more than 5seconds, or more than 10 seconds, but when the average rate at whichultrasound pulses is generated is increased, it is increased morequickly, for example, it may be increased back to the original ratewithin 1 second. The average rate at which ultrasound pulses aregenerated may be increased again (for example back to the average rateof main operating mode) without waiting to complete an ultrasound frame.

It may be that in at least some circumstances (e.g. in at least one saidmode in which the average rate at which ultrasound pulses are generatedhas been reduced) the images displayed by the ultrasound apparatusfreeze and/or the ultrasound measurement data is frozen (e.g. the sameultrasound frame data is repetitively transmitted). This enables animage to continue to be displayed while the average rate of ultrasoundpulse generation (e.g. the number of scan lines in each ultrasoundframe, more generally the number of scan positions per ultrasound frame)drops below a level suitable for displaying a high quality image, butenables movement to be detected (at which point the average rate ofultrasound pulses generation increases and an image of sufficientquality can be generated again).

It may be that the receive circuitry is sensitive to the frequency ofultrasound in received ultrasound echoes. It may be that the ultrasoundmeasurement data comprises received ultrasound frequency data, ormovement (e.g. velocity) data derived therefrom. It may be that the saidultrasound frequency data, or movement data derived therefrom, isprocessed to determine an amount of movement of the ultrasound probe. Afrequency shift (Doppler shift) caused by movement of the probe may bedetected.

Nevertheless, it may be that the ultrasound measurement data does notinclude received ultrasound frequency data, or data derived therefromsuch as or Doppler shift (D-mode ultrasound) measurements. Typically, itis a parameter relating to the intensity of ultrasound echoes which isprocessed to determine whether the one or more inactivity criteria aremet. Thus, movement can be detected without the additional complexityand cost of Doppler mode ultrasound detection.

Typically the ultrasound measurement data (e.g. ultrasound data that isprocessed) is not ultrasound image data, that is to say it has not beenprocessed to form a two dimensional image, for example it has typicallynot been subject to scan conversion. By an ultrasound image we refer toa visual representation, in at least two dimensions, of the scan regionas indicated by the ultrasound echoes which are received by theultrasound probe, in response to ultrasound signals being generated bythe ultrasound probe. Ultrasound image data is derived from ultrasoundmeasurement data (typically by a process including scan conversion). Byprocessing measurement data, prior to image generation, powerconsumption can be further reduced. This is because ultrasound imagegeneration is significantly power intensive. It may be that theultrasound scanner does not generate image data; instead, ultrasoundimage data may be generated by a separate ultrasound data processor.Thus, it may be that the ultrasound scanner can detect inactivitywithout a requirement to generate ultrasound image data (which istypically power intensive).

However, in some embodiments data derived from ultrasound measurementdata, typically ultrasound image data, is processed to determine theamount of movement of the ultrasound probe. The strength of ultrasoundechoes at scan positions (or position interpolated therebetween, e.g.the positions represented by specific pixels), position of features inthe images etc. can be analysed to determine movement using motiondetection algorithms.

The ultrasound scanner may be a (typically handheld) ultrasound probe(comprising at least one battery). However, the ultrasound scanner maycomprise both a first scanner portion (e.g. a scanner body, such as abody worn component) and an ultrasound probe, typically connected to thescanner by a cable. In that case, a temperature sensor, if present, maybe in the scanner body.

The ultrasound probe is typically a handheld probe, i.e. configured tobe used while held in a single hand by a user. The ultrasound scannercomprises one or more batteries. Typically the ultrasound scanner (andthereby the one or more ultrasound sources and receivers) is poweredonly by the one or more batteries in operation. Power consumption is animportant consideration in ultrasound scanners powered only by one ormore batteries within the scanner. It may be that the ultrasound scannerdoes not comprise a fan. Reducing power consumption can make it morepractical to omit a fan, thereby providing a more rugged product.

The ultrasound scanner may be part of ultrasound apparatus which furthercomprises an ultrasound data processing configured to process ultrasoundmeasurement data to generate ultrasound images of the scan region. Themethod may comprise further processing the ultrasound measurement datato generate ultrasound images and then outputting the ultrasound images.Generating ultrasound images typically comprises scan conversion.Generating ultrasound images may comprise one or more of: anglecompounding, frame smoothing and boundary detection. The image processormay comprise a scan converter. The image processor may comprise one ormore of: an angle compounder, a frame smoother and a boundary detectionmodule.

It may be that the ultrasound scanner further comprises a wirelesstransmitter configured to wirelessly transmit the ultrasound measurementdata. The ultrasound scanner may comprise a data compressor configuredto process the ultrasound measurement data and a wireless transmitterconfigured to wirelessly transmit the ultrasound data in compressedform.

The invention extends in a third aspect to ultrasound apparatuscomprising the ultrasound scanner of the first aspect and an ultrasounddata processor, the ultrasound data processor comprising:

-   -   a wireless receiver configured to receive the ultrasound        measurement data transmitted by the wireless transmitter, and    -   an image processor configured to process decompressed data        output by the data decompressor to form ultrasound images of the        scan region, and    -   a display interface (and typically also a display, although the        display interface may be a video data output interface for use        with a separate display) configured to output the ultrasound        images formed by the image processor.

In embodiments where the ultrasound measurement data is transmitted incompressed form, the wireless receiver is configured to receive theultrasound measurement data in compressed form and the ultrasound dataprocessor further comprises a data decompressor configured to decompressthe compressed ultrasound measurement data received by the wirelesstransmitter.

The invention also extends in a fourth aspect to methods according tothe second aspect of the invention further comprising transmitting theultrasound measurement data through a wireless transmitter to a wirelessreceiver of an ultrasound data processor, and at the ultrasound dataprocessor, processing the ultrasound measurement data to form ultrasoundimages of the portion of the subject, and outputting the ultrasoundimages (for example displaying the ultrasound image or outputting videodata through an interface). It may be that the method comprises the stepcarried out at the ultrasound scanner of compressing the ultrasoundmeasurement data, wherein the ultrasound measurement data istransmitting through a wireless transmitter to a wireless receiver of anultrasound data processor in compressed form and the method comprisesthe further step carried out by the ultrasound data processor ofdecompressing the received compressed ultrasound measurement data, andprocessing the resulting decompressed ultrasound measurement data toform ultrasound images of the portion of the subject.

Accordingly, in some embodiments the ultrasound measurement data iscompressed prior to being transmitted through a wireless communicationschannel comprising the wireless transmitter and the wireless receiver.The compressed ultrasound measurement data is then decompressed and usedto generate images. The ultrasound measurement data may be compressedusing a variable length code.

The wireless transmitter and receiver are typically radio transmittersand receivers. Typically, they are radio transceivers. It may be thatthe wireless transmitter and receiver are Wi-Fi transmitters andreceivers (e.g. Wi-Fi transceivers). Thus, the compressed data may betransmitted by Wi-Fi. Wi-Fi is a wireless radio transmission protocolspecified by the IEEE 802.11 standards. (Wi-Fi is a trade mark of theWi-Fi Alliance).

The one or more ultrasound sources and receivers may be in the form ofan array. The array of ultrasound sources and receivers is typically inthe form of a one dimensional array, for example spaced apart along alinear or curved line. The scan region is typically planar (being across-section through a region of a subject, in use). The scan region istypically defined by the configuration of the ultrasound sources andreceivers, and the transmit circuitry and beam processor.

The ultrasound scanner typically comprises a controller which regulatesthe rate at which scan positions are scanned. The ultrasound scannertypically comprises at least one processor and memory which stores aprogram which causes the at least one processor to function as thecontroller when executed. The transmit circuitry, the receive circuitry,the beam former, (and/or the data compressor where present) and/or thecontroller may be formed in whole or in part by the processor executinga program stored in the memory. Dedicated transmit circuitry, receivercircuitry and beam former ICs are known in the art.

The ultrasound data processor typically comprises one or more processorsand memory storing program code. The ultrasound data processor may be ahandheld electronic device, for example a smartphone, tablet or laptop.The image display may be in wired communication with the imageprocessor. However, the image display may be in wireless communicationwith the image processor, for example the image display may comprisevideo glasses in wireless communication with the image processor. Theimage processor (and/or data decompressor where present) may beimplemented in whole or in part by a microprocessor of the ultrasounddata processor executing program code stored in a memory. The imageprocessor may be implemented in whole or in part by a graphic processor.

One skilled in the art will appreciate that although the one or moreultrasound sources and receivers may comprise ultrasound sources andseparate ultrasound receivers, the one or more ultrasound sources andreceivers may comprise or consist of ultrasound transducers, for examplepiezoelectric transducers or capacitive transducers, which function asboth ultrasound sources and receivers.

The apparatus and method may be used to scan a region of an animal,typically a non-human animal, for example a farm animal (e.g. a pig,horse, cow or sheep) or a domestic animal (e.g. a cat or a dog).

The invention extends in a fifth aspect to an (e.g. veterinary)ultrasound scanner, the ultrasound scanner comprising:

-   -   an ultrasound probe which comprises one or more ultrasound        sources and receivers,    -   at least one battery,    -   at least one temperature sensor,    -   transmit circuitry configured to apply electrical signals to the        ultrasound sources to generate ultrasound pulses and transmit        them into a scan region,    -   a controller configured to regulate the transmission of        ultrasound pulses into the scan region by the ultrasound source        and to reduce the average rate at which ultrasound pulses are        generated responsive to the temperature measured by the at least        one temperature sensor exceeding a (first) threshold.

The invention extends in a sixth aspect to a method of operating an(e.g. veterinary) ultrasound scanner, the ultrasound scanner comprising:

-   -   an ultrasound probe which comprises one or more ultrasound        sources and receivers,    -   at least one battery,    -   at least one temperature sensor,    -   transmit circuitry configured to apply electrical signals to the        ultrasound sources to generate ultrasound pulses and transmit        them into a scan region,    -   the method comprising measuring a temperature within the        ultrasound scanner using the at least one temperature sensor        and, responsive to detecting that the measured temperature        exceeds a (first) threshold, reducing the average rate at which        ultrasound pulses are generated.

The ultrasound scanner typically also comprises:

-   -   receive circuitry configured to measure ultrasound echoes        received at the ultrasound receivers from the scan region, and    -   a beam processor configured to process the measured ultrasound        echoes and output ultrasound measurement data. Typically the        ultrasound measurement data comprises measurements of ultrasound        echoes from each of a series of scan positions in the scan        region,

It may be that the method comprises increasing (and it may be that thecontroller is configured to increase) the average rate at whichultrasound pulses are generated again responsive to the temperaturemeasured by the at least one temperature sensor dropping below a(second) threshold. The second threshold may be lower than the firstthreshold.

The average rate at which ultrasound pulses are generated may be reducedas set out above in respect of the first and second aspect of theinvention. For example, there may be a main operating mode (e.g. adefault mode or a mode determined wholly or in part by user settings) inwhich there is a predetermined average rate at which ultrasound pulsesare generated. When the average rate at which ultrasound pulses aregenerated is reduced, that is typically relative to that main operatingmode.

The average rate at which ultrasound pulses are generated may be reduced(e.g. relative to a main operating mode) by one or more of:

-   -   reducing the number of scan lines (e.g. per ultrasound frame);    -   increasing the period between ultrasound frames;    -   periodically stopping generating ultrasound pulses for a period        of time and then restarting.

It may be that the average rate at which ultrasound pulses are generatedis reduced progressively, for example step-wise, responsive to themeasured temperature reaching progressively increasing values (e.g.progressively increasing thresholds). It may be that the average rate atwhich ultrasound pulses are generated is reduced through a plurality ofdifferent modes, which differ in the average rate at which ultrasoundpulses are generated, in a predetermined order. The modes may forexample differ in terms of one or more of: the number of scan lines perultrasound frame and/or the period between ultrasound frames.

Optional feature disclosed in respect of any aspect of the invention areoptional features of each aspect of the invention and in particularfurther optional features of the fifth and sixth aspects of theinvention correspond to the optional features disclosed in respect ofthe first and second aspects of the invention.

DESCRIPTION OF THE DRAWINGS

An example embodiment of the present invention will now be illustratedwith reference to the following Figures in which:

FIG. 1 is a block diagram of ultrasound apparatus including anultrasound probe;

FIG. 2 is a flow diagram of an ultrasound apparatus operating procedure;and

FIG. 3 is a schematic diagram of scan positions located along scan lineswithin a scan region;

FIG. 4 is a schematic diagram of ultrasound measurement data; and

FIG. 5 is a flow chart for a procedure for reducing the average rate ofgeneration of ultrasound pulses.

DETAILED DESCRIPTION OF AN EXAMPLE EMBODIMENT

With reference to FIGS. 1 to 3, the invention relates to a hand-heldultrasound scanner 2 which is used with a separate ultrasound dataprocessor 4, together forming ultrasound imaging apparatus. Theapparatus is used to generate ultrasound images of a scan region of ananimal and to display these images to the user in real time so that theuser can rapidly and accurately carry out a scanning task.

In the example of FIG. 1, the ultrasound scanner 2 has a body 5 and aseparate handheld ultrasound probe 3, which is the part that is pressedagainst an animal's flesh in use and which contains the ultrasoundtransducers 24. The ultrasound probe is connected to the body 5 by acable. In alternative embodiments, the ultrasound scanner is anintegrated ultrasound probe device, with an ultrasound probe region atone end, having the ultrasound transducers, and configured to behandheld.

The ultrasound scanner 2 comprises a processor (e.g. a CPU) executing astored program, functioning as the controller 20. The controllerregulates the scanning procedure, including pulse generation, and dataprocessing and transmission. The controller includes a movementdetection module 38 which may take the form of program code stored inmemory executed by the same processor as the controller.

The ultrasound scanner has a one-dimensional (curved or straight line)array of ultrasound transducers 24 and a transmit beamformer 22(comprising the transmit circuitry) which generates electrical signalsin use to drive the ultrasound transducers to generate ultrasound pulsesfocussed in turn on specific scan positions 6 along scan lines 8 withina scan region 10. Typically pulses are focussed along individual scanlines and thereby pass the scan positions within that line in turn. Thescan lines and scan positions are defined relative to the position ofthe array of ultrasound transducers by the timing and phase of theultrasound pulses which are generated, and by the configuration ofreceive beamformer 26 (functioning as the beam processor and comprisingthe receive circuitry) which is configured to extract ultrasound pulseechoes from measurements made by the ultrasound transducers.

The scanner also comprises a beamformed data processor 28 configured tocarry out standard data processing steps on raw ultrasound data such asband-pass filtering, detection and log compression and to outputultrasound measurement data 29. An optional compressor module 30 isconfigured to receive and compress ultrasound measurement data output bythe beamformed data processor and there is a Wi-Fi transceiver 32(functioning as the wireless transmitter), having a transmit buffer 34,for transmitting (optionally compressed) ultrasound measurement datafrom the compressor module in use.

The scanner has one or more internal (replaceable or integral) batteries35 (optional rechargeable) which supplies all of the power to thescanner during use. The scanner may also have an interface for receivingpower from an external source (e.g. a power cable) but external powersources may often be unavailable.

The ultrasound data processor 4 which is used with the ultrasound probecomprises a Wi-Fi transceiver 40 which functions as a wireless receiverand a decompression module 42 configured to decompress compressedultrasound measurement data received from the Wi-Fi transceiver (whererequired). Wi-Fi is a wireless radio transmission protocol specified bythe IEEE 802.11 standards. (Wi-Fi is a trade mark of the Wi-FiAlliance).

An image processor 44 is provided to calculate ultrasound image datafrom the ultrasound measurement data is coupled to a display interface46 which transmits images to the display screen 50 in use for display.The ultrasound data processor has a display screen 50. In someembodiments video generated by the ultrasound data processor isadditionally or alternatively displayed on a remote display, for exampleon goggles worn by a user.

The ultrasound data processor may be a dedicated computing device or asmart phone or tablet running a suitable application program, such as aniPhone, iPad or other iOS device (iPhone, iPad and iOS are trade marksof Apple Inc.) or a mobile telephone or tablet executing the Androidoperating system (Android is a trade mark of Google Inc.).

One skilled in the art will appreciate that the extent to which thefunctionality of the components of the ultrasound scanner and ultrasounddata processor are implemented as standalone circuits or as program codeinstructions executed by a processor is a matter of design choice. Forexample, the compressor and decompressor (where present) might beimplemented by a processor executing program code or with dedicatedcircuits. The transmit beamformer, receive beamformer and Wi-Fitransceivers include dedicated circuitry but may be implemented in partby the processor.

In embodiments in which the ultrasound scanner comprises both a body 5and an ultrasound probe 3 the distribution of the components shown inFIG. 1 between the body and probe is a matter of design choice. Some orall of the transmit and receive circuitry, for example, may be in theultrasound probe along with the transducers.

With reference to FIG. 2, during operation the controller 20 regulatesthe transmit beamformer to generate 100 ultrasound pulses which arefocussed in turn on scan positions 6 spaced apart along the length ofscan lines 8 in the scan region 10. Ultrasound echoes are received 102by the ultrasound transceiver array and beamformed 104. The controllerregulates the rate at which ultrasound frames are scanned, the number ofscan lines in each ultrasound frame and the number of positions in eachscan line where ultrasound pulses are focussed and from which ultrasoundechoes are received and measured. In this way, the controller determinethe average rate at which ultrasound pulses are generated. One skilledin the art will be aware of standard ultrasound techniques forcontrolling transmit and receive beamformers to scan the scan positions.

Thus, the ultrasound scanner transmits ultrasound pulses from a numberof transducers, synchronised to focus on individual scan positions, atvarying depths within individual scan lines, and repeats the process toscan line across the scan region which is effectively a slice through aregion of interest. The process is then repeated to rescan the region ofinterest. The data concerning each scan through the region of interestis an ultrasound frame. There is a standard ultrasound frame rate,number of scan lines and number of scan positions per scan line, therebydetermining a standard rate of generation of ultrasound pulses, referredto herein as the main operating mode. The ultrasound frame rate, numberof scan lines and number of scan positions per scan line in the mainoperating mode may be preprogrammed and/or depend on user instructions.

The beamformed data is pre-processed 106 by the beamformed dataprocessor 28. This step includes data processing steps which aretypically carried out on raw beamformed ultrasound measurement data suchas band-pass filtering, detection and log compression. The beamformeddata processor processes data concerning individual frames one at a timeand within each frame processes data concerning individual scan linesone at a time.

The output from the beamformed data processor is ultrasound measurementdata 29, which is broken down into ultrasound frame data portions 60,each of which relates to a successive ultrasound frame. An ultrasoundframe data portion comprises a plurality of scan line data structures62. Each scan line data structure relates to echoes received atdifferent depths within individual scan lines. In this example, the scanline data is a measurement of echo brightness with depth (z) in aspecific scan line. The scan line data structure also includes meta-dataindicating to which slice the measurement data relates, for example itmay specify an x and y position (relative to the transceiver array),angle, line length and number of scan points and/or distance betweenscan points.

The ultrasound measurement data is analysed 120 as it is generated todetermine whether there is inactivity. This is discussed further below.

The ultrasound measurement data is also compressed 110 by, for eachultrasound frame, and then for each scan line, calculating thedifference between consecutive measurements within the scan line datastructure and then encoding these differences with a variable lengthcoding algorithm (e.g. one based on a Huffman code). Data generated bythe data compression module is passed to the Wi-Fi module for wirelesstransmission 110 to the image processor. The compressed data is storedin the transmit buffer of the Wi-Fi module until it is transmitted.

The compressed data is received 112 by the Wi-Fi module of the imageprocessor. The decompression module 42 then decompresses the receivedultrasound measurement data, by reversing the variable length encodingprocess to recreate the ultrasound measurement data. The imageprocessing module 44 then processes the decompressed ultrasoundmeasurement data and carries out typical ultrasound image generationprocedures 116 known to the person skilled in the art, such as scanconversion, angle compounding frame smoothing, boundary/edge detectionand so forth, and generate pictures, being individual image frames forconsecutive display on a display 46 of the image processor. The imageprocessor may be the microprocessor which functions as the controller(the CPU of the device) however video processing may be carried out witha dedicated graphics processing unit, for example using OpenGL withindividual scan lines represented as OpenGL polygons.

The resulting images are then displayed on the display screen 50 oroutput through a video output interface. The images are displayed inreal time, within 0.25 s of the ultrasound measurements which gave riseto the images. The user can therefore manoeuvre the ultrasound probe toview a region of interest of an animal and obtain real time visualfeedback.

While the probe is being used, the ultrasound measurement data 29 whichis generated is analysed by the movement detection module 38, forexample when the measurement data for each ultrasound frame is complete.The ultrasound measurement data is analysed to determine if theultrasound measurement data is consistent with the probe not beingmoved. The measurement data from one frame is stored and when themeasurement data for the next frame is available, it is compared withthe stored data. For each scan position for which there are measurementsin both frames, the values of those measurements are compared. Thedifferences are averaged and if the differences are less than apredetermined threshold (being an example of an inactivity criteria), itis determined that there is inactivity.

If inactivity continues to be detected for a predetermined period oftime then the controller 20 controls the transmit circuitry to reducethe average rate of generation of ultrasound pulses, thereby reducingpower consumption.

With reference to FIG. 5, the ultrasound probe is initially scanning inthe main operating mode 200. Once inactivity has been detected 202 asdescribed above for a predetermined period of time, which may be asshort as 1 second, for example, the ultrasound probe moves to a firstreduced power operating mode 204 in which the ultrasound frame rate isreduced. In an example, the ultrasound frame rate is halved. The numberof scan lines in each ultrasound frame and the number of scan positionsremain the same. Thus, the rate of generation of ultrasound pulseshalves.

If inactivity continues to be detected 206 for a further period of time(e.g. a further second), the ultrasound probe moves to a second reducedpower operating mode 208 in which the ultrasound frame rate is reducedagain, in an example to one tenth of its original rate. The number ofscan lines in each ultrasound frame and the number of scan positionsremain the same. Thus, the rate of generation of ultrasound pulses isnow 10% of the original rate.

If inactivity continues to be detected 210 for a further period of time(e.g. a further second), the ultrasound probe moves to a third reducedpower operating mode 212 in which the ultrasound frame rate remains thesame but number of scan lines is reduced. In an example, the number ofscan lines is halved. Thus, the rate of generation of ultrasound pulsesis now 5% of the original rate.

In some embodiments, alternate scan lines are scanned in a firstultrasound frame, and then the scan lines which were omitted in thefirst ultrasound frame are scanned in the following ultrasound frame.This is then repeated. This means that an image can still be generatedon an ongoing basis despite the reduction in scanning. This is generallyacceptable because this only takes place when there has been minimalmovement for a period of time.

If inactivity continues to be detected 214 for a further period of time(e.g. a further second), the ultrasound probe moves to a third reducedpower operating mode 216 in which the ultrasound frame rate and thenumber of scan lines are reduced still further, for example by a furtherfactor of eight each. In this background scanning mode, ultrasoundpulses are generated only with a view to detecting when the probe ismoved again. In the third reduced power operating mode, the imagesdisplayed to a user stop being updated and remain the same. This can beachieved either by transmitting a message to the ultrasound image dataprocessor to freeze the images, or simply by transmitting the same,previously measured ultrasound measurement data repetitively to theultrasound image data processor. This is acceptable because it has beendetected that the ultrasound probe is not moving. If the user iscontinuing to view the display it is likely that they want the image tostay the same.

In due course it will be detected 218 that the inactivity criteria is nolonger met because the ultrasound probe is being moved again. When thishappens, and whichever reduced power operating mode the device is in atthe time, the controller switches straight to the main operating mode,possibly even during an ultrasound frame. Once a user starts to move theprobe again it is likely that they want to continue to move the probeand obtain real time images straight away.

Thus, the power consumption of the transmit circuitry, and therefore theultrasound probe, is reduced when the ultrasound probe is inactive. Itdoes not matter that rapidly updated images are not provided to the userbecause it is detected that they are not moving the ultrasound probesignificantly.

In an alternative low power operating mode, the ultrasound frame rateremains reasonably high, potentially as high as in the main operatingmode, but the number of scan lines is reduced to minimal (e.g. one).This may be advantageous over the third reduced power operating modedescribed above in some circumstances as it may allow movement to bedetected more quickly when it occurs.

One skilled in the art will appreciate that inactivity could bedetermined in various different ways, for example:

-   -   The ultrasound measurement data from one ultrasound frame may be        processed to detect one or more features within the scan region        (e.g. boundaries, internal cavities, or points of unusually        strong or weak echoes). This might be determined from a        characteristic high value of, or low value of, or change in        measurement strength between adjacent scan positions in a scan        line. A corresponding analysis may be carried out on ultrasound        measurement data from a subsequent ultrasound frame. If the        corresponding one or more features are in the same place, or        very close, it is determined that there is inactivity.    -   The measurement of ultrasound echoes at a plurality of (e.g. all        or a subset of) scan positions within the ultrasound measurement        data relating to a single frame can be processed to determine        some characteristic parameters, for example, calculating an        average value (e.g. arithmetic mean, median, mode, geometric        mean), variance, standard deviation or range. The same        parameters may be calculated for a subsequent frame. If the        parameters remains the same or similar to within a predetermined        threshold, it is determined that there is inactivity.

It is generally sufficient only to consider a subset of scan lines todetect inactivity (and later to detect activity).

In some embodiments, the number of scan positions per scan line may alsobe reduced (e.g. in one or more reduced power modes). However, inembodiments where the scan positions within a scan line aredifferentiated between solely on the basis of the timing of receivedechoes, without requiring separate ultrasound pulses to be generated foreach scan position in the scan lines, this will have a minimal effect onpower consumption.

In an example, the ultrasound probe also comprises a temperature sensor37, which may be a standalone temperature sensor or built into otherfunctionality, for example, integrated into a processor, or part of afan control circuit. If the temperature sensor measures a temperaturewhich exceeds a threshold, the power expenditure can be reduced byswitching to one of the reduced power operating modes, until themeasured temperature return to below the threshold (or a lowertemperature threshold).

The ultrasound scanner has a separate standby mode. The scanner entersthe standby mode when it detects that there are no ultrasound echoesfrom the ultrasound pulses. This indicates that the probe is no longerin contact with an animal's flesh. In this case, the ultrasound scannergoes into a very much lower power mode. No ultrasound frame data istransmitted in the standby mode. In the standby mode, the scannergenerates ultrasound pulses occasionally, e.g. every 200 ms, and thescanner powers up again if ultrasound echoes are detected.

In an alternative embodiment, the scan converted ultrasound image datais processed, instead of, or as well as, the ultrasound measurementdata, to determine whether there has been inactivity. Again, inactivitycan be determined by detecting that specific features have not moved, ornot moved by more than a threshold. Inactivity can be determined bycomparing consecutive images, or parts thereof. The scan convertedultrasound image data can later be processed to determine that there isactivity again, or the ultrasound measurement data can be processed todetermine that there is activity again (e.g. if the average rate ofgeneration of ultrasound pulses is sufficiently low that a high qualityimage can no longer be formed).

1. An ultrasound scanner comprising: an ultrasound probe which comprisesone or more ultrasound sources and receivers, at least one battery,transmit circuitry configured to apply electrical signals to theultrasound sources to generate ultrasound pulses and transmit them intoa scan region, receive circuitry configured to measure ultrasound echoesreceived at the ultrasound receivers from the scan region, a beamprocessor configured to process the measured ultrasound echoes andoutput ultrasound measurement data, the ultrasound measurement datacomprising measurements of ultrasound echoes from each of a series ofscan positions in the scan region, and a controller configured toregulate the transmission of ultrasound pulses into the scan region bythe ultrasound source and to process the ultrasound measurement data, ordata derived therefrom, to determine an amount of movement of theultrasound probe, and to reduce the average rate at which ultrasoundpulses are generated responsive to the determined amount of movement ofthe ultrasound probe meeting at least one inactivity criterion.
 2. Anultrasound scanner according to claim 1, wherein the amount of movementof the ultrasound probe is determined by analysing changes in theultrasound measurement data, or data derived therefrom, between repeatedmeasurements of the same scan positions.
 3. An ultrasound scanneraccording to claim 2, wherein at least one inactivity criteria comprisesthat a measure of changes in the strength of ultrasound echoes betweenmeasurements of ultrasound echoes from one or more correspondingpositions is below a threshold, optionally for at least a predeterminedperiod of time.
 4. An ultrasound scanner according to claim 3, whereinthe at least one inactivity criteria comprises that the position of oneor more features within the scan region determined from the ultrasoundmeasurement data, or data derived therefrom, relative to the ultrasoundprobe, has moved by less than a threshold amount, optionally over atleast a predetermined period of time and/or wherein the at least oneinactivity criteria comprises that a measure of a change in a propertyof the strength of ultrasound echoes at a plurality of scan positions inthe ultrasound measurement data is less than a predetermined threshold,optionally for at least a predetermined period of time.
 5. An ultrasoundscanner according to claim 1, wherein the average rate at whichultrasound pulses are generated is reduced by one or more of: reducingthe number of scan lines; increasing the period between ultrasoundframes; and/or periodically stopping generating ultrasound pulses for aperiod of time and then restarting.
 6. An ultrasound scanner accordingto claim 1, having a main operating mode in which there is apredetermined average rate at which ultrasound pulses are generated, andthat in the main operating mode, ultrasound measurement data, or dataderived therefrom, relating to a first number of scan positions isprocessed to determine whether the at least one inactivity criterion ismet but that in at least one mode with a reduced average rate ofgeneration of ultrasound pulses, a second, lower number of scanpositions is processed to determine whether the at least one inactivitycriterion, or at least one activity criterion, is met.
 7. An ultrasoundscanner according to claim 1, wherein, the controller is configured toincrease the average rate at which ultrasound pulses are generated againresponsive to the determined amount of movement of the ultrasound probemeeting at least one activity criterion.
 8. An ultrasound scanneraccording to claim 7, wherein when the average rate at which ultrasoundpulses are generated is reduced, the average rate at which ultrasoundpulses are generated is reduced progressively but when the average rateat which ultrasound pulses is generated is increased, it is increasedmore quickly.
 9. Ultrasound apparatus comprising an ultrasound scanneraccording to claim 1 and an ultrasound data processor, the ultrasounddata processor comprising: a wireless receiver configured to receive theultrasound measurement data transmitted by the wireless transmitter, andan image processor configured to process decompressed data output by thedata decompressor to form ultrasound images of the scan region, and adisplay interface configured to output the ultrasound images formed bythe image processor.
 10. A method of operating an ultrasound scanner,the ultrasound scanner comprising an ultrasound probe which comprisesone or more ultrasound sources and receivers, the method comprising: theone or more ultrasound sources and receivers generating ultrasoundpulses and receiving ultrasound echoes from a scan region, processingmeasurements of the received ultrasound echoes to thereby calculateultrasound measurement data, the ultrasound measurement data comprisingmeasurements of ultrasound echoes from each of a series of scanpositions in the scan region, and processing the ultrasound measurementdata, or data derived therefrom, to determine an amount of movement ofthe ultrasound probe, if the amount of movement of the ultrasound probethereby detected meets at least one inactivity criterion, reducing theaverage rate at which ultrasound pulses are generated.
 11. A methodaccording to claim 10, wherein the amount of movement of the ultrasoundprobe is determined by analyzing changes in the ultrasound measurementdata, or data derived therefrom, between repeated measurements of thesame scan positions.
 12. A method according to claim 10, furthercomprising transmitting the ultrasound measurement data through awireless transmitter to a wireless receiver of an ultrasound dataprocessor, and at the ultrasound data processor, processing theultrasound measurement data to form ultrasound images of the portion ofthe subject, and outputting the ultrasound images.
 13. An ultrasoundscanner, the ultrasound scanner comprising: an ultrasound probe whichcomprises one or more ultrasound sources and receivers, at least onebattery, at least one temperature sensor, transmit circuitry configuredto apply electrical signals to the ultrasound sources to generateultrasound pulses and transmit them into a scan region, and a controllerconfigured to regulate the transmission of ultrasound pulses into thescan region by the ultrasound source and to reduce the average rate atwhich ultrasound pulses are generated responsive to the temperaturemeasured by the at least one temperature sensor exceeding a threshold.